Loads on a rotating shaft can deform the shaft and affect the way the shaft rotates in the one or more bearing assemblies that support the shaft. FIG. 3a shows an example of an unloaded shaft 320 which is supported by two bearing assemblies 310. FIG. 3b, shows the shaft 320 bending away from an unloaded state 302 due to the presence of a central load 304 (the load need not be centered; off-center loads will also bend the shaft). Rotating masses 330 at the ends of the shaft, with or without an additional center load 304, will cause the shaft to bend in still another manner when it rotates. This rotating bending of the shaft 320 due to the rotating masses 330 and the resulting shaft-pin rotating bending at the ends of the shaft is shown in FIG. 3c. 
Shaft deformations can produce deformations inside the bearing assemblies, and this in turn can increase wear and consequently lead to a shorter bearing service life.